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b=qecqNptHMtRlwI6Q23NBhTSoSqWmvJUhM1iwbAU9rT0a7PDjS6DiszunK1elfMT8+ eKYpNOg2Gzw14Xr0Nxs295tyYPKBUhMjnAsvMR209NgkI16WfJ0QRlFlyToIOHOlOO rLLyCxRC1i+OAmfRaeFU5+M/lLSNNRKWqXY1LaAl8p4gMKxOhkDHIK5F2pyn3Gp0zB iFRb3aFnwJ3n4jbggG9gTtXUls5FBNDc0eLJ3PLZbHVIoZ0w6Sg6MT2oamtaG1F5Eg Re7/AVvpCgmX9ZpzHDDj1suyyNbvwqVfIoAEbf9JPuJKrU/K8YneLJFs3Bug+ly7dc vpULjqGpH123A== From: SeongJae Park To: Liew Rui Yan Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [RFC PATCH v6] mm/damon: add synchronous commit for commit_inputs Date: Fri, 27 Mar 2026 06:59:38 -0700 Message-ID: <20260327135939.4085-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260327062558.66392-1-aethernet65535@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 2459C20003 X-Stat-Signature: 5tnbyc3pp875fu5i9tqqxwgzos8r6jqa X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774619981-57581 X-HE-Meta: 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 3RlS0ks/ 5NE17R3h7e09D8cpYBZEoTyEstNGwBxXGc72M/zVJFvzgrEqkw0RxpSLMPeaZKpaAnAdfd8td2UdJ0EAXw7Ms26NctxmR0082Uj4yiaS/Iq3V/7C6GNxIErFsBalOtsNlGxvAzfFPC2Xagke0+tbqhTJvGR/IBcFaulEUepw37N6lZvrmqflIvW0OknQxHX8cDWxHGXqzLCKNVT1m2wPK2URaJpFIN9+fD6CHpaNYFgN2eQAGx9bVc452QcZoH+E64jx60UsCcBIsCtFH96zojrBhaiaSPl52qaesGgnkbRw5zMk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Liew, On Fri, 27 Mar 2026 14:25:58 +0800 Liew Rui Yan wrote: > Problem > ======= > Writing invalid parameters to sysfs followed by 'commit_inputs=Y' fails > silently (no error returned to shell), because the validation happens > asynchronously in the kdamond. > > Solution > ======== > To fix this, the commit_inputs_store() callback now uses damon_call() to > synchronously commit parameters in the kdamond thread's safe context. > This ensures that validation errors are returned immediately to > userspace, following the pattern used by DAMON_SYSFS. > > Changes > ======= > 1. Added commit_inputs_store() and commit_inputs_fn() to commit > synchronously. > 2. Removed handle_commit_inputs(). > > This change is motivated from another discussion [1]. > > [1] https://lore.kernel.org/20260318153731.97470-1-aethernet65535@gmail.com > > Signed-off-by: Liew Rui Yan > --- > Changes from RFC-v5: > - Removed unnecessary assignment in commit_inputs_store(). > - Return -EINVAL instead of -EBUSY when 'commit_inputs' is triggered > while kdamond is not running. > - Link to RFC-v5: https://lore.kernel.org/20260325013939.18167-1-aethernet65535@gmail.com > > Changes from RFC-v4: > - Rename the 'yes' variable in commit_inputs_store() to the more > understandable 'commit_inputs_request'. > - Return -EBUSY instead of -EINVAL when 'commit_inputs' is triggered > while kdamond is not running. > - Link to RFC-v4: https://lore.kernel.org/20260323021648.6590-1-aethernet65535@gmail.com > > Changes from RFC-v3: > - Added checks for 'ctx' and 'damon_is_running()' to prevent NULL > pointer dereference during early boot. (Found by Sashiko.dev) > - Removed handle_commit_inputs() and its associated polling logic as > they have become dead code after moving to the synchronous damon_call() > approach. > - Ensure the 'commit_inputs' is properly updated. > Link to RFC-v3: https://lore.kernel.org/20260322231522.32700-1-aethernet65535@gmail.com > > Changes from RFC-v2: > - Removed damon_validate_attrs(), now using damon_commit_ctx() for > synchronous validation in the kdamond context. > - Following DAMON_SYSFS pattern for synchronous commit via damon_call(). > - Link to RFC-v2: https://lore.kernel.org/20260321140926.22163-1-aethernet65535@gmail.com > > Changes from RFC-v1: > - Remove question from commit message area. > - Added synchronous validation for DAMON_RECLAIM. > - Rename damon_valid_attrs() -> damon_validate_attrs(). > - Exported a new function damon_validate_attrs() and declared it in > damon.h. > - Link to RFC-v1: https://lore.kernel.org/20260321002642.22712-1-aethernet65535@gmail.com > > mm/damon/lru_sort.c | 42 +++++++++++++++++++++++++++++++++++------- > mm/damon/reclaim.c | 42 +++++++++++++++++++++++++++++++++++------- > 2 files changed, 70 insertions(+), 14 deletions(-) > > diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c > index 554559d72976..453033f3cb3e 100644 > --- a/mm/damon/lru_sort.c > +++ b/mm/damon/lru_sort.c > @@ -39,7 +39,6 @@ static bool enabled __read_mostly; > * the re-reading, DAMON_LRU_SORT will be disabled. > */ > static bool commit_inputs __read_mostly; > -module_param(commit_inputs, bool, 0600); > > /* > * Desired active to [in]active memory ratio in bp (1/10,000). > @@ -349,18 +348,47 @@ static int damon_lru_sort_apply_parameters(void) > return err; > } > > -static int damon_lru_sort_handle_commit_inputs(void) > +static int damon_lru_sort_commit_inputs_fn(void *arg) > { > + return damon_lru_sort_apply_parameters(); > +} > + > +static int damon_lru_sort_commit_inputs_store(const char *val, > + const struct kernel_param *kp) > +{ > + bool commit_inputs_request; > int err; > + struct damon_call_control control = { > + .fn = damon_lru_sort_commit_inputs_fn, > + .repeat = false, Undeclared fields are initialized to zero. I don't think we need to explicitly set repeat here. > + }; > > - if (!commit_inputs) > + err = kstrtobool(val, &commit_inputs_request); > + if (err) > + return err; > + > + if (!commit_inputs_request) > return 0; > > - err = damon_lru_sort_apply_parameters(); > - commit_inputs = false; > - return err; > + /* > + * Skip damon_call() during early boot or when kdamond is > + * not running to avoid NULL pointer dereference. > + */ > + if (!ctx) > + return -EINVAL; > + > + err = damon_call(ctx, &control); > + > + return control.return_code; Shouldn't we return err if it is not zero? [...] > --- a/mm/damon/reclaim.c > +++ b/mm/damon/reclaim.c Same comments can be applied to changes for this file. Thanks, SJ [...]